Typhoid fever is an acute illness associated with fever caused by the Salmonella typhi bacteria. It can also be caused by Salmonella paratyphi, a related bacterium that usually causes a less severe illness. The bacteria are deposited in water or food by a human carrier and are then spread to other people in the area.

Typhoid fever is contracted by the ingestion of the bacteria in contaminated food or water. Patients with acute illness can contaminate the surrounding water supply through stool, which contains a high concentration of the bacteria. Contamination of the water supply can, in turn, taint the food supply. About 3%-5% of patients become carriers of the bacteria after the acute illness. Some patients suffer a very mild illness that goes unrecognized. These patients can become long-term carriers of the bacteria. The bacteria multiplies in the gallbladder, bile ducts, or liver and passes into the bowel. The bacteria can survive for weeks in water or dried sewage. These chronic carriers may have no symptoms and can be the source of new outbreaks of typhoid fever for many years.

The incubation period is usually one to two weeks, and the duration of the illness is about four to six weeks. The patient experiences

• poor appetite,
• headaches,
• generalized aches and pains,
• fever,
• lethargy, and
• diarrhea

People with typhoid fever usually have a sustained fever as high as 103 to 104 degrees Fahrenheit (39 to 40 degrees Celsius).

Chest congestion develops in many patients, and abdominal pain and discomfort are common. The fever becomes constant. Improvement occurs in the third and fourth week in those without complications. About 10% of patients have recurrent symptoms (relapse) after feeling better for one to two weeks. Relapses are actually more common in individuals treated with antibiotics.

After the ingestion of contaminated food or water, the Salmonella bacteria invade the small intestine and enter the bloodstream temporarily. The bacteria are carried by white blood cells in the liver, spleen, and bone marrow. The bacteria then multiply in the cells of these organs and reenter the bloodstream. Patients develop symptoms, including fever, when the organism reenters the bloodstream. Bacteria invade the gallbladder, biliary system, and the lymphatic tissue of the bowel. Here, they multiply in high numbers. The bacteria pass into the intestinal tract and can be identified for diagnosis in cultures from the stool tested in the laboratory. Stool cultures are sensitive in the early and late stages of the disease but often need to be supplemented with blood cultures to make the definite diagnosis.

Medical and travel history
Your doctor is likely to suspect typhoid fever based on your symptoms and your medical and travel history. But the diagnosis is usually confirmed by identifying S. typhi in a culture of your blood or other body fluid or tissue.

Blood or body fluid or tissue culture

For the culture, a small sample of your blood, stool, urine or bone marrow is placed on a special medium that encourages the growth of bacteria. In 48 to 72 hours, the culture is checked under a microscope for the presence of typhoid bacteria. A bone marrow culture often is the most sensitive test for S. typhi.

Antibody and antigen testing
Your doctor may recommend other tests to help diagnose typhoid fever, such as:

• Enzyme-linked immunosorbent assay (ELISA). This blood test looks for an antigen that's specific to typhoid bacteria. An antigen is any substance, such as a virus, bacterium, toxin or foreign protein, that triggers an immune system response in your body. An ELISA test can identify if you carry the disease, but not whether you have an active infection.
• Fluorescent antibody test. This test checks for antibodies to S. typhi. Antibodies are proteins produced by your immune system in response to harmful substances (antigens). Each antibody is unique and defends your body against a single antigen.

Typhoid fever is treated with antibiotics which kill the Salmonella bacteria. Prior to the use of antibiotics, the fatality rate was 20%. Death occurred from overwhelming infection, pneumonia, intestinal bleeding, or intestinal perforation. With antibiotics and supportive care, mortality has been reduced to 1%-2%. With appropriate antibiotic therapy, there is usually improvement within one to two days and recovery within seven to 10 days.

Several antibiotics are effective for the treatment of typhoid fever. Chloramphenicol was the original drug of choice for many years. Because of rare serious side effects, chloramphenicol has been replaced by other effective antibiotics.

The carrier state, which occurs in 3%-5% of those infected, can be treated with prolonged antibiotics. Often, removal of the gallbladder, the site of chronic infection, will cure the carrier state.

Intestinal bleeding or perforation
The most serious complication of typhoid fever — intestinal bleeding or perforation — may develop in the third week of illness. About 5 percent of people with typhoid fever experience this complication.

Intestinal bleeding is often marked by a sudden drop in blood pressure and shock, followed by the appearance of blood in your stool.

Other possible complications include:

- Inflammation of the heart muscle (myocarditis)

- Pneumonia

- Inflammation of the pancreas (pancreatitis)

-Kidney or bladder infections

- Infections of the spine (osteomyelitis)

- Infection and inflammation of the membranes and fluid surrounding your brain and spinal cord (meningitis)

- Psychiatric problems such as delirium, hallucinations and paranoid psychosis

With prompt treatment, nearly all people in industrialized nations recover from typhoid. Without treatment, some people may not survive complications of the disease.

• Wash your hands. Frequent hand washing is the best way to control infection. Wash your hands thoroughly with hot, soapy water, especially before eating or preparing food and after using the toilet.

• Avoid drinking untreated water. Contaminated drinking water is a particular problem in areas where typhoid is endemic. For that reason, drink only bottled water or canned or bottled carbonated beverages, wine and beer. Carbonated bottled water is safer than uncarbonated bottled water is. Wipe the outside of all bottles and cans before you open them. Ask for drinks without ice. Use bottled water to brush your teeth, and try not to swallow water in the shower.

• Avoid raw fruits and vegetables. Because raw produce may have been washed in unsafe water, avoid fruits and vegetables that you can't peel, especially lettuce. To be absolutely safe, you may want to avoid raw foods entirely.

• Choose hot foods. Avoid food that's stored or served at room temperature. Steaming hot foods are best. And although there's no guarantee that meals served at the finest restaurants are safe, it's best to avoid food from street vendors — it's more likely to be contaminated.